The invention relates to a portable handheld work apparatus such as a motor-driven chain saw, brushcutter or the like.
An internal combustion engine is provided for driving the work tool in a portable handheld work apparatus. The engine is accommodated within a housing of a drive unit of the work apparatus. A carburetor for metering fuel is also disposed in the housing and the carburetor is connected to a fresh air/fuel mixture inlet of the engine. Furthermore, an air filter is provided which is mounted ahead of the carburetor in the flow direction of the fresh air/fuel mixture and cleans the combustion air inducted by the engine. Finally, a fuel tank is mounted within the housing of the drive unit for supplying fuel to the carburetor and therefore to the engine.
A conventional arrangement of the parts within the housing of the drive unit as known up to now is described in U.S. Pat. No. 4,793,303. Here, the air filter lies above the carburetor which is connected to the cylinder of the engine, that is, the air filter lies on the side of the carburetor facing away from the crankcase of the engine. The air filter is, in this way, mounted next to the outer wall of the housing of the drive unit whereby easy accessibility of the air filter is provided for the exchange of filter material as required.
Arrangements of the air filter directly next to the carburetor are also known. In one such air filter arrangement, as described in U.S. Pat. No. 6,227,162, a round filter is seated on a support formed in the air filter housing with the round filter being within an air filter housing. This support defines an extension of the air channel of the carburetor.
It is an object of the invention to provide a work apparatus which is improved in such a manner that the largest possible filter effect is obtained with a compact configuration of the drive unit.
The portable handheld work apparatus of the invention includes a motor-driven chain saw and a brushcutter and includes: a drive unit housing; an internal combustion engine mounted in the drive unit housing and having an inlet for conducting an air/fuel mixture into the engine; a carburetor for metering fuel; an air filter mounted in the housing upstream of the carburetor for receiving a flow of air; the carburetor being connected to the inlet of the engine and metering fuel to form the air/fuel mixture; a fuel tank mounted in the housing; the carburetor and the fuel tank conjointly defining a space therebetween; and, the air filter having an air filter housing disposed in the space so as to lie partially below the carburetor.
According to a feature of the invention, a housing of the air filter is provided which lies partially in a space between the carburetor and the fuel tank. The fuel tank is arranged in the drive unit at a spacing to the carburetor. The carburetor lies next to the cylinder head of the engine which is especially advantageous when utilizing four-stroke internal combustion engines. With the arrangement of the air filter below the carburetor (that is, between the carburetor and the fuel tank), a very compact configuration of the drive unit can be achieved whereby the manipulability of the work apparatus is improved. If a larger air filter is required, then the housing of the air filter can expand into a region next to the carburetor.
With the arrangement of vibration-dampening means, the housing of the air filter is advantageously arranged as an isolated vibration system within the housing of the drive unit. It is practical to hold the housing of the air filter on an inner wall of the housing of the drive unit with the interposition of the vibration damping means in the form of an anti-vibration element. This inner wall separates the engine from the air filter. The inner wall then partitions the inner space of the drive unit housing into two parts whereby the engine is separated from the air filter. The housing of the air filter is supported on the inner wall via the anti-vibration element.
The housing of the air filter is partitioned into a contaminant space and a clean space by a filter element mounted in the air filter. The clean space of the housing is provided in the space region lying at the elevation of the carburetor. The clean space can extend into the region disposed between the carburetor and the fuel tank. The filter element can be configured essentially flat or planar and is advantageously exchangeable from the end face of the drive unit. For this purpose, an opening is provided in the housing of the drive unit at the elevation of the air filter lying next to the housing wall. An arrangement of the air filter in a drawer-like component which can be pulled out of the drive unit is also practical.